A concern in the design of turbo-machines such as steam turbines is the accommodation of thermal distortion or deflections, particularly during transient events. For example, seals within a steam turbine may include a number of teeth on a stationary component that interlace with lands on a rotating component. The radial gaps between the stationary components and the rotating components are designed to be as narrow as possible so as to minimize steam leakage. Deflection of the shell may cause the rotating components to come in contact with the stationary seals. Specifically, seal clearances between the rotating components and the stationary components may close in at the base and tend to open in the cover of the shell in a phenomenon referred to as humping. If the extent of the humping is severe enough, undesirable rubbing and component damage may occur.
Steam turbine shells generally may be supported by a number of shell arms extending axially about both ends of the shell in a direction parallel to the rotor. Turbine humping may be intensified in that the support arms largely may act as pivot points. Moreover, the shell arms also may experience thermal gradients therein so as to cause further deflections.
There is thus a desire for an improved turbo-machine such as a steam turbine with enhanced accommodation for thermal distortions, particularly during transient events. Such an improved turbo-machine may eliminate or reduce turbine humping so as to facilitate smaller radial seal clearances for improved overall performance and efficiency. Moreover, eliminating or reducing the opportunities for turbine humping also should facilitate longer component lifetime with reduced wear and damage.